The present invention relates to a staple gun that includes a safety assembly electrically on a front end of the nose of the staple gun and connected to an electromagnetic valve which is cooperated with a trigger assembly.
A conventional staple gun is shown in FIG. 1 and generally includes a handle 1xe2x80x2 with a main passage 11xe2x80x2 which is connected to a source of air from a compressor (not shown) and a barrel is connected to the handle 1xe2x80x2 with a chamber 10xe2x80x2 defined in the barrel. A cylinder 24 is received in the barrel 10xe2x80x2 and an end mount assembly 2xe2x80x2 is connected to a rear end of the barrel and a nose is connected to a front end of the barrel. An end cap 22 is movably connected to an inside of the end mount assembly 2xe2x80x2 and biased by a spring 22 so as to seal an open end of the cylinder 24 in which a piston 25 is movably received in the cylinder 24. A magazine for receiving staples is connected to the nose. A recess 12xe2x80x2 is defined in a wall of the handle 1xe2x80x2 and a trigger valve 4 is received in the recess and can be activated by a trigger 5xe2x80x2. Pressurized air may enter the recess 12xe2x80x2 via a gap between the valve 4 and the opening in the wall of the handle 1xe2x80x2 and enters a tube 3xe2x80x2 engaged with a hole 14 defined in an inside of the handle 1 and a path 20xe2x80x2. The pressurized air enters a space between the end cap 22 and the end mount assembly 2xe2x80x2 via the path 20xe2x80x2 so that the opening of the cylinder 24 is sealed by the end cap 22 by the pressure in the space and the spring 21.
Referring to FIGS. 2 and 3, when a safety plate 55 is pushed toward the trigger 5xe2x80x2 and the trigger 5xe2x80x2 is squeezed, the shaft of the trigger valve 4 is shifted to seal the opening communicating with the recess 12xe2x80x2 and the pressure in the space mentioned above is reduced so that the end cap 22 is pushed toward the end mount assembly 2xe2x80x2 by the pressure in the main passage 11xe2x80x2. Once the end cap 22 is moved to open the open end of the cylinder 24, the piston 25 is moved to eject a staple by a plate connected to the piston 25 from the nose. Air in the cylinder 24 is pushed out via orifices defined through the wall of the cylinder 24 into the chamber 10xe2x80x2. Referring to FIG. 4, after shooting, the trigger 5xe2x80x2 is released and the air in the chamber 10xe2x80x2 enters the cylinder 24 again to push the piston 25 back to its original position. Simultaneously, air in the main passage 11xe2x80x2 enters the tube 3xe2x80x2 and the path 20xe2x80x2 to assist the spring 21 to move the end cap 22 to seal the open end of the cylinder 24 again.
The safety plate 55 and the trigger 5xe2x80x2 are exposed and protrude from the barrel of the staple gun so that they could be tangled by other object or activated unintentionally.
The present invention intends to provide a staple gun wherein the safety assembly is located at a distal end of the nose and connected to an electromagnetic valve so that the staple gun can be activated only when the safety assembly and the trigger both are operated.
In accordance with one aspect of the present invention, there is provided a staple gun which comprises a barrel and a cylinder is received in the barrel. A piston is movably received in the cylinder and a nose is connected to a front end of the barrel. A plate connected to the piston extends through the nose. An end mount assembly is connected to a rear end of the barrel and an end cap movably seals an open end of the cylinder and a spring is biased between the end cap and an inside of the end mount assembly.
A handle is connected to the barrel and a main passage is defined in the handle. The main passage communicates with a chamber in the barrel. A first opening and a second opening are respectively defined through a wall of the handle and respectively communicate with two recesses. A trigger valve and an electro-magnetic valve are respectively engaged with the two recesses. The trigger valve has a first shaft which movably seals the first opening and the elecro-magnetic valve has a second shaft which movably seals the second opening A trigger is connected to the first shaft so as to push the first shaft to seal the first opening.
A safety tube is movably mounted to a distal end of the nose and has a first sensor located at an end thereof A second sensor is located at nose and located corresponding to the first sensor. The second sensor is electrically connected to the electro-magnetic valve so as to move the second shaft to seal the second opening.